The situation at the Fukushima Daiichi nuclear power plant in Japan is far from being under control. And no one should downplay the triple catastrophe in Japan—a failing nuclear power plant on top of an earthquake and a tsunami that claimed at least 10,000 lives. But U.S. government officials, as well as some outside experts, say there is no reason to expect that harmful radioactive emissions from the crippled reactors will reach the United States. That means there’s no reason to stockpile or take potassium iodide pills.

The Union of Concerned Scientists, a well-regarded organization in Cambridge, Mass., that describes itself as nuclear safety watchdog, explained why this way:

While wind patterns will likely carry the radioactive plume eastward, since Japan is thousands of miles from the United States, radioactive material in the air will be so diffuse by the time it reaches Hawaii, Alaska, or the mainland United States that it is highly unlikely to create significant health concerns.

The U.S. Environmental Protection Agency (EPA) has been posting data from radiation monitors. You can check out graphical representations of that data by clicking hereand then clicking on the pink and blue dots on the map (if you have a slower computer, some of the graphs may be slow in loading). A monitor in Hawaii did detect radioactive atoms (isotopes) last week that might have originated at the Fukushima plant. Even so, all the monitors are showing radiation levels that are fluctuating at normal background levels.

Yet Americans have been buying up potassium iodide to protect themselves against radiation that they fear is coming over from Japan—or to get ready for a nuclear power plant accident here.

I spoke with Dr. Richard Zane about the situation. Dr. Zane is vice chair of the emergency department at Harvard-affiliated Brigham and Women’s Hospital and medical director for emergency preparedness for Partners Healthcare in Boston.

Q: Should people in United States be taking potassium iodide pills?

A: There is zero indication that any Americans should be taking potassium iodide.

Q: Why?

A: Any radiation being emitted from the plant itself is exceedingly unlikely to reach the United States and if it does, it will be so little as to pose no risk. In addition to other factors, radiation decreases as a function of distance.

So the only way anyone in the United States would be exposed would be through radioactive fallout—radioactive particles floating across the Pacific Ocean and then settling on areas in the United States. The fires and explosions at Fukushima plant have released some radioactive material into the air. But it would take a much, much larger catastrophe for radioactive material emitted in Japan to travel 5,000 miles and reach this country in concentrations that would be at all consequential.

Even if weather conditions were just right—meaning no rain, since rain would wash radioactive particles out of the atmosphere—not nearly enough material has been released from Fukushima for it to reach the United States, including Alaska and Hawaii, in amounts that are close to being harmful.

Q: Is there is any danger to take potassium iodide?

A: Potassium iodide can cause gastrointestinal distress and make you feel pretty unwell. And the extra iodine can be a problem for people with thyroid conditions like Graves disease and autoimmune thyroiditis.

Q: Some people are buying up potassium iodide now in case of nuclear accident closer to home. Does that make sense?

A: Not really. Hoarding it could create shortages. Besides, potassium iodide is not an anti-nuclear panacea or a cure. It protects just the thyroid gland, not the rest of the body.

Q: So what is the best way to protect yourself in case of a nuclear emergency?

A: If there were a nuclear emergency near where you live, the best way to protect yourself is probably notgoing out to get potassium iodide. The best strategy is to get a significant distance from the source of the radiation. That is why we have evacuation plans for areas near nuclear power plants, and it’s the reason Japanese officials have taken the important step of evacuating people from the area around Fukushima nuclear power plant.

If evacuation isn’t feasible or advised, then the next best thing to distance is putting a barrier between yourself and the radiation. As a practical matter, that means staying inside with the windows and doors closed. Walls and closed windows would block some of the radiation. Staying inside also helps prevents contact with radioactive particles.

If you do come into contact with radiation or radioactive particles, you should take off any clothes you are wearing and wash off in a shower as soon as possible.

Personal and family preparedness for any type of disaster is very important. The basics are to organize a kit, make a plan, and be informed. I recommend the government Web site, www.ready.gov

Q: Do you have potassium iodide pills at home?

A: I live in the suburbs outside of Boston about 50 miles from the nearest nuclear power plant in Plymouth, Mass. and no, I do not have any potassium iodide pills at home. It’s exceedingly unlikely that I will need them and there simply is no reason for me to have any. I do however have a kit, a plan and am informed.